Nuclear Transplantation (Cloning)
Overview Nuclear transplantation is a form of cloning. This is a delicate process that is a major hurdle in the development of cloning technology (1). This method involves relocating the nucleus of a donor cell to another cell in which it has been enucleated (2). This process has helped scientists and embryologists to manipulate the development of an organism, nuclear potency, cell de-differentiation, chromatin structure/function, epigenetics and genome manipulation (2,3). Somatic Cell Nuclear Transfer (SCNT) Somatic cell nuclear transfer is a laboratory technique by which one creates a viable embryo from a body cell and an egg cell (4). Examples of certain somatic cell types (body cells) that replace the nucleus are from the skin, heart or nerve cell (1). This process allows the newly implanted nucleus to fuse with the oocyte and cause the somatic nucleus to reprogram to a pluripotent state through electric shock (1). This technique is used for both therapeutic and reproductive cloning (4). It is being utilized in stem cell research and has answered the many issues concerning embryonic stem cell research (4). The aim of carrying out this procedure is to obtain pluripotent cells from a cloned embryo, which then can be used in therapies and disease research(4). U_U History The idea of nuclear transplantation was first written about by Yves Delage in 1895 (2). He speculated that if someone were to replace the egg nucleus with a different egg nucleus then the egg would be able to fully develop (2). In 1938 a man named Hans Spemann suggested an experiment using nuclear transplantation but it wasn’t Hans to perform the first nuclear transfer but two men: Thomas King and Robert Briggs (2). Thomas King and Robert Briggs demonstrated the transferred nuclei had produced viable tadpoles, which thus became the foundation for later cloning procedures (6). This technique was later on used by a scientist named Ian Wilmut and Keith Campbell which led to the famous first cloning of a mammal named “Dolly” the sheep in 1996 (2,5). BRILL The Sheep Dolly was the famous primary example of a successful somatic cell cloning of a mammal. Dolly was a female sheep cloned by Ian Wilmut and Keith Campbell. She was born on July 5 1996 and had passed away from a progressive lung disease five months before her seventh birthday. She has three mothers; one provided the egg, another DNA, and last carried the cloned embryo. The making of Dolly had proved that a healthy clone can be made by taking a cell from a specific part of the body and that it could recreate a whole individual (5). After Dolly, other large mammals were cloned such as pigs, deer, horses and bulls. Creating cloned animals is inefficient and Dolly was the only offspring to survive into adulthood. It was announced by Wilmut that this technique of cloning may never be sufficient to use in humans (5). Caveats Nuclear transplantation is not a 100% effective technique to use. As said prior, cloning animals has shown to be inefficient and that Dolly the sheep was the only offspring from nuclear transplantation to survive into adulthood. How could that be? Well, first off, it isn't fully understood if the transplantation will take effect. They have seen that genomic reprogramming is the process by which cloning is possible. The issue is that there is little understanding in which reprogramming factors are involved in the oocyte accepting the new nucleus and if it will occur when the transplantation takes place. (1) References 1. Nuclear Transfer. Wikipedia. http://en.wikipedia.org/wiki/Nuclear_transfer 2. Cohmer, Sean. Nuclear Transplantation. The Embryo Project Encyclopedia.(2011-06-14). ISSN: 1940-5030 http://embryo.asu.edu/pages/nuclear-transplantation 3. Galli c. et al. Introduction to cloning by nuclear transplantation. PubMed. http://www.ncbi.nlm.nih.gov/pubmed/14733742 4. Somatic-cell Nuclear Transfer. Wikipedia. http://en.wikipedia.org/wiki/Somatic-cell_nuclear_transfer#The_Process 5. Dolly (Sheep). Wikipedia. http://en.wikipedia.org/wiki/Dolly_(sheep) 6. Cohmer, Sean, "Thomas Joseph King Jr. (1921-2000)". Embryo Project Encyclopedia (2012-01-01). ISSN: 1940-5030 http://embryo.asu.edu/pages/thomas-joseph-king-jr-1921-2000